//
// Created by wze-zero on 2024/9/13 013.
//
#include <iostream>

using namespace std;

int main() {
    int n;
    long m = 0, sum = 0;
    cin >> n;
    for (int i = 1; i < n + 1; ++i) {
        m += i;
        sum += m;
    }
    cout << sum << endl;
    return 0;
}